Centrifugal pumps are widely used in a variety of fluid transport applications. A rotating impeller is driven by an internal or external power source, drawing liquid into a pump chamber, and expelling liquid therefrom at increased pressure. In the most typical configuration, liquid flows into an axial inlet of the impeller, is forced by the impeller through a toroidal flow path formed by a volute surrounding the impeller, and is discharged from the volute and out of the pump.
Access to the interior of the volute and the impeller is occasionally needed, for inspection, repair, or to clear out debris trapped between the volute and impeller. The latter instance is somewhat common wherein the pump is used in a temporary application, such as e.g., emptying a water heater, draining a swimming pool cover, or irrigation. Such water is often somewhat dirty and may contain pieces of solid material such as grit, scale, small wood scraps, or construction debris. It is preferable that such a pump be easy to partially dismantle at the installed location, without disconnecting the pump from the piping, drive motor and/or wiring thereto, or removing the entire assembly to a remote location for service.
It is also preferable that such a pump be “self priming”, in that there is often a need to install such a pump in a location that is above the level of the liquid to be pumped. Hence, one cannot rely upon gravity-driven flow to flood the inlet of the pump and thereby prime the pump. Self-priming capability is typically accomplished by providing fluid passageways in the pump that result in recirculation of a small amount of liquid through the volute of the pump, until the “prime”, i.e. the complete filling of the volute with liquid phase, is accomplished or re-established. During this period of recirculation, air or any other gas present that is drawn into the pump inlet is caused to move through the volute and out through the discharge outlet of the pump.
In general, self priming centrifugal pumps incorporate a recirculation port in the volute that is too small to deliver to the impeller all of the water that it is capable of discharging. With the pump impeller being “starved” for adequate liquid, the air (or other gas present) is drawn from the suction opening of the pump by the impeller. The resultant mixture of froth (gas and water) is repeatedly discharged by the impeller and into the surrounding pump chamber. The froth in the pump chamber separates so that the majority of the gas is discharged from the outlet of the pump chamber. The liquid returning to the recirculation port by gravity therefore is relatively free of gas. This liquid is mixed, entrained, and/or otherwise dispersed with more gas flowing in through the pump inlet, and the resulting froth is discharged out through the volute whereupon it separates into liquid and gas. The pump effectively becomes an air pump temporarily, moving air in the pump inlet, and out the pump outlet, while repeatedly recirculating liquid contained in the pump chamber. This cycle continues until a continuous flow of liquid is established at the pump inlet, containing substantially no entrained gas.
During the period of time when “self priming,” i.e. internal recirculation is occurring, there is a risk that heat buildup may occur within the pump volute and chamber. Of particular concern is the buildup of heat at the pump shaft seal, where a thin film of liquid provides lubrication between a rapidly rotating first surface, and a stationary second surface. Current self-priming centrifugal pumps in general do not provide prolonged wetting, cooling, and lubrication of the pump shaft seal, and failure thereof during a prolonged period of self priming is a problem.
Portable transfer pumps are also often exposed to a variety of adverse environmental conditions, such as heat, cold, and rain or snow. Such pumps are further subjected to generally rough handling, being repeatedly moved from job site to job site, often unprotected and exposed to the elements. Finally, since the use of such pumps is in applications that are not high precision, high “value added” tasks, it is necessary that such pumps be made inexpensively in order to sell at a relatively low price.
U.S. Pat. No. 6,471,476 of Diels et al., issued Oct. 29, 2002, discloses a centrifugal trash pump comprising a volute and an impeller that are disposed in a pump chamber accessible through an access opening in the front wall of the pump casing. The access opening is closed by a cover attachable to the front wall of the casing. The volute is attached to the cover by fasteners accessible from the outside of the cover so as to permit the cover and volute to be removed either as a unit or individually, with the cover being removed first, followed by the volute. The entire disclosure and figures of U.S. Pat. No. 6,471,476 is incorporated herein by reference.
The pump of Diels et al. does provide self-priming capability, and the ability to easily access the impeller and interior of the volute therein. However such pump comprises a rather complex multi-piece casing, volute, and cover assembly and combination of fasteners that is quite likely expensive to manufacture. The disclosure of Diels et al. is silent with regard to lubrication and cooling of the pump shaft seal during prolonged periods of self-priming.
There is therefore a need for a simple portable transfer pump that will reliably operate in self priming mode for a prolonged period, that has a simple, easily and inexpensively manufactured construction, that is resistant to adverse environmental conditions, and that is easy to service, maintain, and/or repair.
It is therefore an object of this invention to provide a portable transfer pump that can operate in self priming mode for prolonged time periods without damage to the pump shaft seal.
It is an object of this invention to provide a portable transfer pump that provides adequate cooling and lubrication to the pump shaft seal during regular and during self priming operation.
It is a further object of this invention to provide a portable transfer pump that provides superior cooling of the motor thereof during operation.
It is another object of this invention to provide a portable transfer pump that comprises a simple, one-piece housing that is of high strength and primarily of cast construction.
It is an object of this invention to provide a portable transfer pump that is aesthetically attractive and substantial in appearance.
It is a further object of this invention to provide a portable transfer pump with easy access to the impeller and volute thereof.
It is a further object of this invention to provide a portable transfer pump having an electrical switch incorporated therein, and a long power cord attached thereto.
It is a further object of this invention to provide a portable transfer pump with a housing having a pump cavity filling funnel incorporated therein.
It is a further object of this invention to provide a portable transfer pump with a plug engaged with a pump cavity filling funnel, and requiring no tools for removal of such plug from such filling funnel.
It is a further object of this invention to provide a portable transfer pump to which can be fitted common pipe and/or hose fittings.
It is a further object of this invention to provide a portable transfer pump comprising a large handle cast into the housing that renders the pump well balanced to assist in transportation thereof.
It is a further object of this invention to provide a portable transfer pump having a unitary multi-functional housing cover that serves to replace a large number of related parts needed in a typical pump.
It is a further object of this invention to provide a portable transfer pump wherein the critical components thereof are well protected from adverse elements and rough handling.
It is a further object of this invention to provide a portable transfer pump that is lightweight.
It is a further object of this invention to provide a portable transfer pump that is portable and is certified for outdoor use by various certifying and regulatory agencies and government entities.
It is a further object of this invention to provide a portable transfer pump having an integrally molded fastener in the impeller thereof.